1. Field of the Invention
The present invention concerns plants for the production of metal articles through the feeding of molten metal under pressure from a holding furnace to a die positioned on a surface of a press located on the furnace.
2. Description of the Related Art
At present many metal articles, for example the rims of vehicle wheels, are produced through the forced injection of molten metal into a die. Molten metal is usually kept in holding furnaces. A hydraulic press is positioned on top of the holding furnace and, on a lower plane of the press, a die is provided which communicates with the bottom of the holding furnace through a vertical duct. The furnace is pressurized with compressed air so that the molten metal is conveyed upward along the duct until reaching the die and filling it.
Molten metal is periodically introduced into the holding furnace through an appropriate opening provided with a door. Since the furnace is pressurized with compressed air, the door must ensure a perfect seal. For this purpose, the door is provided with a gasket made of a suitable heat-resistant material, which, however, wears out due to repeated use and must be periodically replaced.
At present, the doors of holding furnaces comprise a simple panel hinged to the furnace, which is lifted either for the introduction of new molten metal into furnace itself or for the replacement of the gasket. These doors present a series of drawbacks, since the opening and closing mechanism exerts an asymmetrical pressure on the gasket and does not ensure a perfect seal, thus making it necessary to change the gasket frequently. Furthermore, due to such opening and closing systems, maintenance operations on the door and/or on the charging hole and/or the gasket are neither quick, nor simple to carry out.
The subject of the present invention is a new automatic door for molten metal holding furnaces which is provided with a double opening/closing and tilting mechanism for the replacement of the gaskets and/or the maintenance of the door and the charging hole. The new door for holding furnaces simplifies the opening and closing operations, ensures easy and precise maintenance of the door and/or the charging hole and also allows the gasket of the door to be easily changed, and furthermore no special external equipment is required to open, close or tilt the door.
The new automatic door comprises a fixed plate with charging and inspection hole integral with the furnace itself, a moveable closing panel with replacement gasket, two rotary guides, two parallel lever systems that press the closing panel against the furnace mouth, two adjusting mechanisms, a hydraulic cylinder that provides for the sliding movement of the closing panel and two hydraulic cylinders operating the lever systems that press the closing panel.